Pneumatic spring.



JQHOFMANN.

PNEUMATIC SPRING.

APPLICATON FILED APR. 13, 1914. 1 151 591. Patented Aug. 31, 1915.

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Wil/nemen v I J. HOFMANN. PNEUMA'TIC SPRING. APPLICATION FILED APR. I3, 1914.l

Patented Aug. 31, 1915.

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f Qnameo uns ms l JOSEF HOFMANN, OF MONT PELER-IN, ASXlTZXEIRLATD.

FNEUMATIC SPRING.

T0 all wir om t may conce/rw Be it known 'that l, Josur I-lomi'ANN, a citizen of the Republic of Switzerland, residing at Mont lelerin, Switzerland, have invented certain new and useful improvements in Pneumatic Springs and 1 do hereby declare the following to be a full, clear, and exact description of the invention, suoli as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanyino* drawings, and to letters orviigures of reference marked thereon, which form a part of this specification. i

My invention relates ,to pneumatic springs or shock absorbers for vehicles and is of the well known type in which a liexible dia phragm is secured within a rigid casing, mounted in fixed relation to the vehicle body, and cooperating with a plunger' which is Connected with the running gear of the vehicle.

In known existing springs of this type.

the plungers are provided with stems orV bodies which are slidably mounted in stationary guide members, and any displacement between the vehicle body and the running gear will cause a. lateral. displacement or twisting between the sliding elements of the spring, which will result in a binding of said elements. This binding not only prevents a satisfactory operation of the spring, but speedily results in a wearing out of the parts thereof.

The object of this invention is to overcome these defects and to provide a pneumatic spring designed especially for use on automobiles of the standard types, but whose features of construction are susceptible of embodiment in other forms of vehicles; and to. this end my invention consists in the cylinder, diaphragm, plunger and support for the latter havingv the construction and a-rrangement substantially as hereinafter set forth.

i In making my invention, my aim has heen to solve the problem of the binding of the elements, and this I have accomplished by providing a structure wherein all sliding contact between the parts of the pneumatic spring and all sliding motion between the Steel springs and the above mentioned spring Specification of Letters Patent. :Partant-(gd *lngs 31, 1915, Application :tiled April 1o, 1914. Serial No. 881,494.

are eliminated.' The elimination is effected by connecting the ends of the steel springs to the plunger supporting levers in such a manner that there is no sliding motion between these connections and consequently there is no sliding contz'ict, due to lateral thrusts of the running gear and car frame nor between the plunger' and cylinder as in the known constructions where the pneumatic spring is connected to the ends of the steel springs. i

lVhile in the present device the plungers may be supported directly on the vehicle axle, l have provided means for connecting the plungers with the vehicle springs in a way as to secure a perfectguide for the plunger, as well as for the steel springs, it being important in curves and other side thrusts to further permit large amplitude of the air spring, and still; avoid entirely sliding motion and binding of elements as before mentioned, a function which as l believe has not been accomplished by any ofl the known forms of suspension and which is ot' greatest importance to the free play and flexibility of such a spring and its-durability. l also reduce by this arrangement themovement of the plungers and therefore of the diaphragnis to their half value or even more` and by 'this l increase the life of suchdiaphra gms, which is of great importance and a technical improvement on similar devices. rlhe construction of c 7lii ler f 'ni of i 5 1C o1 plunger, structure of diaphragm, the ope 'i tion of the latter when the plunger works up and down in the'cylinder, also the method of attaching the pneumatic spring to the running gear of the vehicle, l believe to be novel. y

rPhe plunger is guided centrally solely by 'the compressed air itself without any' mechanical means. The reason for this novel function lies in the tendency of compressed air (or other gas) to press equally on. any material or substance exposed to it and therefore seek a balance in its mechanical equivalent. The power in my case, the compressed air, acts upon a diaphragm, the center of which is mounted on a plunger.

If the plunger is once set centrically, the

air will not permit the plunger head to get -shown in the rear portion of Fig. 1.

of a moditied'form of cylinder center, which requires avery great force, the plunger will immediately spring back to its normal center position. By this arrangement a perfectly safe guiding of the plunger head is provided and all sliding contact isA while the, plunger is moving toward the cyl-- vinder head, I so construct the diaphragm,

cylinder and plunger, that the gathering of the fabric of the'tliapl'iragm is effected byl the compressed air itself which forms the dianhra 'm into a `alurahtv of rooves or l g i channels and by so doing reduces the diameter of the diaphragm, which is necessary to permit vthe latter 'to enter the cylinder, the

walls of which it has shortly before beenl touching.

My improvements are capable of applica* tion to various forms of steel spring structures, but it will be snllicient to illustrate the invention to show the same in connection with the well known half and three quarter elliptic steel spring which is the most common form in use yon automobiles.

ln the accompanying drawings-figure 1 is a side view of the front and rear portions of an automobile frame having my improveniente applied thereto. Fig. 2 is an enlarged detail vertical section of the front portion of Fig. 1. Fig. 3 an enlarged Adetail plan view of the supporting lever Fig. t' is a sectional view of Fig. 3. Fig. 5 is a vertical section of the preferred form of dia phragn'i and cylinder. Fig. 6 is a top view of the compressed air cylinder. Fig. 7 is a side view of a modified form of diaphragm; Fig. 8 is a horizontal section on line 8-8 of Fig. 2. `Fig. 9 is a detail sectional view head and securing means therefor.

s shown in Fig. 1 the front and rear springs are semi-elliptic; each front spring 1 is rigidly connected, vin the usual manner, to the front axle 2. the rear end being pivotally connected to a bracket' 8, which is rigidly connected to the side of the automobile frame l.

rllhe front end of the spring 1 is connected by a shackle 5 to the front end of` a yielding plunger support which preferably consists of a rigid lever C hinged at its 'rear end to the front .of the frame et. This provides for an absolutely safe axle guide without sliding motion. The hinge connection I employ between the lever and frame preferably consists, in generahofa bearing member 7, which is bolted to tl: end f the frame et' and projects into a 8 armed in the rear end of the lever (i. The sides of the slot are connected to said bearing by a bolt 9 passing through the overlapping parts near their lower edges as shown in Fig. 2.

The end 10 of the bearing and the opposing end wall 11 of the slot are inclined at diiferent angles to said lower edges so as to permit a sufficient amount of swing to the leve and also to limit the movement of the same.

The pneumatic cylinder' Asupport comprises the frame tand a standard or post 12, which is perpendicular to the frame, is preferably formed integral witli the bearing 7, and has fixed thereto a vertically arranged casing 13, vthe axis of said casing passes through or near the center of the lever (l.

To the interior of Vthe air cylinder 13, near the upper edge thereof, isA fixed a ilexible diaphragm 1-l, the bottoni of which, as shown in Fig. 2, rests on a freely movable plunger 15 whose stem or rod 16 projects through the lower open end of the cylinder 13 and terminates in a spherical lend 17 seated in a socket 18 formed in the lever (i. By making the casing a symmetrical geometric figure in section, I attain an equal distribution of the air pressure on all sides of the plunger so that the air, as before stated serves as a sufiiclent guide for the plunger and consequently all Vcontacting fact that the diaphragm is not taken up and laid onto a rigid surface, it does not get injured as heretofore in known existing devices, but owing to the form of the plunger and the structure of said dialrihragm, the latter bellies under the plunger'.

ln the preferred form, shown in Fig. 5, the diaphragm 14 has a substantially semispherical bottomnnd is preferably made of tire material. To the inner wall of the diaphragm are fixed about twenty-four or more cords 11a, which are about one-eighth of an inch thick and evenly distributed from the top to the bottom of the membrane. The membrane is thrfs `divided into twenty-four sections, each of which takes part in the function of gathering up the fabric. lVhen the piston travels upward and the membrane is turned inside the cylinder, which causes it to follow -the smaller diameter of the piston, each of the twenty-four sections yshrinks to a certain degree before forming tions are composed, is achieved, the fabric cannot be further compressed and it snaps over and begins to form small channels or bellies. When the piston nieves downward each of the twenty-four sections straightens out and expands sufficiently to assume the necessary diameter of the cylinder wall which prevents it from further expansion. The even division and small distance between the twenty-four cords does not allow the fabric to overlap itself and to close a plait under the influence of the air pressure, which would otherwise occur and damage the fabric in a very short time. WVhen this- :form of diaphragm is used, the inner wall of the cylinder 13 is preferably smooth and the plunger head is made in the form of a disk.

To facilitate the taking upof the diaphragm, the interior wallof the cylinder 13 may be corrugated so as to form longitudinalv channels or grooves 19 separated by ribs 20, as shown in Fig. 8.

To correspond with such a cylinder struc` ture, the plunger head may be corrugated as shown in dotted lines Fig. 8, the convex portions 22 of the corrugations being opposite the ribs. 2O of' the cylinder so that the concave portions coperate with the grooves or channels 19 of the cylinder to maintain the channels in the diaphragm and prevent them from flattening, as the lower end of the diaphragm is moved back and forth in the cylinder. In this structure the bellies are formed at the very beginning of' the upward stroke of the plunger without the aid of shrinking or expanding of the material.

The bottom 24 of the diaphragm rests on and may be secured to the plunger head by a screw 25 (Fig. 2). The upper edges of the diaphragms are connected to the cylinder walls by rivets 27.

The diaphragms may be made of tire material, such as canvas impregnated with rubber, several plies of the material being cut into strips and vulcanized together at their longitudinal edges which overlap and form ribs 28, as indicated in Fig. 7. The rivets 2T are vulcanized in these ribs and secured to f thecylinder at the ribs 20. The ribs 28 in the diaphragm also aid in preventing contact between the opposing faces of the diau phragm where the latter is first moved into the cylinder. The diaphragm may also be made of strips of leather connected together. along their longitudinal edges, by steel bands. These bands afford an efficient holding means for the rivets and also serve to prevent contact between the faces of the `diaphragm as above described.

.To render the diaphragm perfectly airtight, l provide a soft rubber lining 2S) or its equivalent, which is secured to the casing by the cover ofl the latter. This lining not only serves to render the diaphragm airtight, but cooperates with the cover to seal the cylinder. l

The cylinder has an inwardly projecting liange 80, formed on its upper end, which flange has recesses 30 at diametrically op posite points for the purposes of admitting the circular cylinder head 31, to be mounted in the cylinder beneath the flange 3() which latter forms an opening of less diameter that the diameter of' the head. As shown in Fig. 5. the upper edge 25). of the lining 29, is slightly longer than the diaphragm and is turned over ont-o the top of the head 31 and is clamped between the latter and the underface of the flange 30. A bolt 32 passes through the' head 3l and thi-(nigh a bridge piece 32 by means of which the head is held firmly in place, said bridge piece hav-` ing filling pieces 32h, which close the recesses 30.

lt will readily be seen. that when compressed air is supplied to the cylinder in thc usual way, the head will be pressed against the edge 29 of the `lining 29 and bind the latter between the head and flange, thus in-A suring a perfectly tight joint-which will prevent the escape of air from the cylinder and the entrance of dust and rain into the latter. i i v A modification of the sealing means above described is shown in Fig. 9 wherein the cylinder head 3la has filling pieces 311 on its top for closing the recesses 3Q. The soft rubber lining here lconsists of a`bag29n having a nipple 29b detachably secured therein. This nipple projects through a. central aperture 31c in the head and througlr an auxiliary cover 31d, seated on the end of the 'cylinder and secured in place by a nut 29c on the end of' the nipple bearing on the cover. An air tube 33, through which airis supplied to the cylinder, is held seated inthe nipple by means of a nut 291 engaging a flange 33u formed on the tube.

F rom the foreging description ofthe conf struction of the parts, it will be understood that the plunger is guided in its movements solely by air in the cylinder4 pressing against the diaphragm.

rlhe plunger rod 1G is preferably held in fixed relation to the plunger head by means of a flange 15 which is formed on the under vof the upper member rests on a horizontal pin 3l which projects through a slot in the lower member of rod. This they is held "springs l placed between said lever against longitudinal displa'e mient by downwardly projecting lugs formed on the ends thereof. The upper member of the rod has a flange 35, formed on its lower edge, for the purpose of affording an abutment capable of being engaged by a lifting lever delsigned for such uses.

lOn automobiles having the three-quarter elliptic springs at the rear, the lower half elliptic spring sections 36,' (one of which is shown in Fig. 1) are usually connected, at their rear ends, to the upper half sections by shackles, which hang below said lower sections. These latter sections are rockable on therear axle 37, which is held against displacement longitudinally of the car by means of a. torsion tube 38 which operates in a well known manner.

In applying my shock absorber to the rear of a car having the above described spring equipment, I connect as usual the front end of each lower half-elliptic spring sections 36 to the car frame 4, by means of a shackle 39, the rear end of each of said sections 36 is connected however', by a shackle 40, to the rear end of a lever 41 which I substitute for the usual upper` quarter elliptical spring section. Each rear lever 41 is pivotally mounted near its front end in a bearing member 42, so as to form a two-armed lever and said bearingmember is rigidly connected by suitable means .to the rear of the car frame 4. rIhis bearing member carries a pneumatic spring or shock absorber of the same construction as the one on the front of the car.l

Owing to the fact that the car body, indicated at 43, usually projects over the rear and is in close proximity tothe upperl spring sections, I have modified the lever 41 to permit the cylinder 13 to be and the cal; body. Ae the space between the lever 41 and the lower end of the cylinder 13 is necessarily small and in order to have the rear plunger rod '16 of suflicient length so as to avoid an excess in the angular movements, I have provided the vfollowing described means for supporting the lower end of said rod.

The lever 41 is formed, at or near the middle of its rear arm with an opening 44 which is oval in forms, as shown in Fig. 3. rThe sides of said opening extend upward into the horizontal plane of the two ends of.

the lever and have bearings, formed in their upper edges, in which are journ'aled trunnions 45 formed in the sides Aof a socket member 4G at the upper end of the latter.

rlhe socket member here shown consists of a cup havingA its walls converging toward its bottom in which is formed asemi-spherical seat 47 for the spherical end 48 of the plunger' rod. This-support not only permits the use of a rod of a length sufficient to mnnmm). the angular movements thereof but it also permits of a universal movement of the rod. To limit the rocking movement of the rear lever 41 I interpose between the latter and the bearing member 42 suitable bumpers 42 which may consist of sockets formed-on the underside of said member at each side of the. pivot point of the lever and adapted to hold soft rubber plugs that may be readily replaced when they become worn by contact with the lever.

To avoid compression in the rear cylinder, I may connect themby pipes 49, with an expansion tank 50 conveniently` mounted at the rear of the car as shown in Fig. 1.

All lateral torsion and twisting of the steel spring section is taken up by the shackle connections between said sections and the pivoted plunger supports. This is of great importance as it will prevent binding of telescoping parts usedinpneumatic springs vof different structure. By this mechanism no matter what lateral deflection or twisting of the steel spring of the vehicle springs takes place, the shackles and the ivoted plunger supports will not be laterally deflected. They will be actuated in the same plane-under all conditions of operation, thereby prevent-ing the lateral displacement or inclination of the plungers while moving in the cylinders, and all frictional wear andbinding between the plunger and the cylinder and also the running gear and the car frame is effectually prevented.

I claiml. In a pneumatic spring, a flexible diaphragm composed of connected divisions said diaphragm thickened along the lines of division thereby controlling the distribution of the folds of the diaphragm when in action.

2.' In a pneumatic spring, a flexible diaphragm uniformly divided into section by neans of a plurality of reinforcing memiers.

3. In a pneumatic spring, a flexible diaphragm uniformly divided into sections by means of a plurality of vreinforcing members uniformly distributed from the top to the bottom of the diaphragm.

4. In a pneumatic spring, a flexible diaphragm divided into sections by a plurality of cords uniformly distributed and attached thereto -from the top to the bottom of the diaphragm. 1

y5. In a pneumatic spring, a diaphragm consisting of a membrane of ltextile material having substantially semi-spherical bottom and divided into sections by a plurality of reinforcing cords uniformly dis` lot ger being yieldingly maintained 4axially of the cylinder under all conditions of operation solely by the air pressure in the cylinder acting on the diaphragn'i, a plunger rod connected to said plunger and means to support said rod.

i'. ln a pneumatic spring. an air cylinder, an unguided plunger therein, and a diaphragm between the cylinder and plunger uniformly divided into sections and arranged to fold over the edge of' the plunger, said plunger' being yieldingly maintained axially of the cylinder under all conditions of operation solely by the lateral air pressure in the cylinder acting on the diaphragm.

8. lo a pneumatic spring, an air cylinder, a phiuger capable of universal movement therein, and a diaphragm between the cylinder and plunger uniformly divided into' section by means of a plurality of reinforcing members uniformly distributed from the top to the bottom of the diaphragnui, for the purpose specified.

9. rlhe combination with a vehicle frame, an air cylinder rigidly connected therewith, and a plunger in the cylinder, of a flexible diaphragm interposed between the cylinder and plunger adapted to solely and yieldingly guide the latter axially of the cylinder, a vehicle spring pivotally connected at one end t said frame, a yielding support connected to the frame and to the spring, and a plunger stern interposed between the plunger and support and pivotally connected with the support between the ends or the latter.

l0. The combination with a vehicle frame, an air cylinder rigidly connected therewith, and a plunger in the cylinder, of a vehicle spring pivotally connected at one end to the frame, a lever pivotedly connected to the frame and to the -vehicle spring, a socket member pivoted in said lever, ano a plunger stem journaled in the socket.

l1. T he combination with a vehicle' frame, an air cylinder rigidly connected therewith, and a plunger in the cylinder, of a vehicle spring pivotally connected at one end to the frame, a lever. pivotedly .connected to the frame and to the vehicle spring, a socket member' journaled in said lever in the plane voi" the ends of the latter and extending below said ends, and a plunger stem resting on the bottom of said. member and universally movable therein.

l2. The combination with a vehicle frame, an air cylinder rigidly connected therewith, and a plunger inthe cylinder, of a vehicle spring pivotally connected at one end to the frame, a lever pivotedly connected to the frameand to the vehicle spring, a cup pivotally mounted in the lever and adapted to swing longitudinally of the latter, and a plunger stem having a. ball and socket connection in the cup.

13. A pneumatic spring comprising a cylinder having a. corrugated interior Wall, a plunger head having a plurality of projectiomrra-liating therefrom, a stem supporting the head. and a flexible diaphragm having loi'igitmlinal ribs formed therein connected to ribs on said interior wall, and resting on said projections.

il. ln a pneumatic spring, an air cylinder having a removable head, a plunger movable in the cylinder free of the wal] thereof, a flexible diaphragm resting on the plunger and connected at its upper end to the cylinder wall, and an inner air-tight lining resting on the diaphragm and having its upper edge connected to the cylinder head.

l5. ln a pneumaticspring, an air cylinder having a removable head, a plunger movable therein free of the cylinder walls, a flexible diaphragm connected at its lower end to the plunger and at its upper edge to the cylinder wall, and an inner air-tight lining resting on the diaphragm and having its upper edge clamped between the underside of an inwardly projecting flange formed on the upper end ot the cylinder and the top of said removable head.

1G. ln a pneumatic spring, an air cylinder having an inwai "lly projecting flange at one Aend and a cylinder head of substantially the same diameter of the cylinder', said flange having' recesses .formed therein at diametrically opposite points for the insertion of the head into the cylinder.

1T. ln a pneumatic spring, an air cylinder having an inwardly projecting flange at one end, a cylinder head or" substantially the same diameter of the cylinder', said flange having recesses formed therein at diametricallv opposite points, and filling pieces for said recesses connected to the head.

18. A pneumatic spring comprising a cylinder, a plunger having a disk-shaped head,

a substantially semi-spherical diaphragm above the plunger and having peripheralv connection with the cylinder, said diaphragm havin'ga plurality of ribs dividing it into sections, and an air tight closure for the cylinder.

19. In a pneumatic spring, a flexible diaphragm composed of narrow connected sections symmetrically arranged to control the folding of the diaphragm.

20. In a pneumatic spring, an air cylinder, an unguidedA plunger therein smaller' than said cylinder, a flexible member inclosing an air cushion between said cylinder and plunger and bellying around said plunger, said plunger being yieldingly maintained axially of the cylinder, under all conditions of operation, solely by the air cushion, a plunger rod for said plunger and means to support the rod While permitting its movement in accordance Wi th the movements of the plunger.

21. In a pneumatic spring, a cylinder, a. plunger therein smaller than the cylinder, a

flexible diaphragm composed of connected sections ine-losing un mr eusluon between the cylinder und plunger and solely mmntmnlng said plunger concentric witli said cylinder,

ln testimony tlmt I claim tlie foregoing as my invention, l have Signed my 'name m presence ot'two subscribing witnesses.

W i tnesse J. W. Asnrmns'r, ll. C. JonoAN. 

